Long-Term Isotope Records of Precipitation in Zagreb, Croatia

Krajcar Bronić, Ines; Barešić, Jadranka; Borković, Damir; Sironić, Andreja; Lovrenčić Mikelić, Ivanka; Vreča, Polona (2020) Long-Term Isotope Records of Precipitation in Zagreb, Croatia. Water, 12 . ISSN 2073-4441

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Abstract

The isotope composition of precipitation has been monitored in monthly precipitation at Zagreb, Croatia, since 1976. Here, we present a statistical analysis of available long-term isotope data (3H activity concentration, delta2H, delta18O, and deuterium excess) and compare them to basic meteorological data. The aim was to see whether isotope composition reflected observed climate changes in Zagreb: a significant increase in the annual air temperature and larger variations in the precipitation amount. Annual mean delta18O and delta2H values showed an increase of 0.017 ‰ and 0.14 ‰ per year, respectively, with larger differences in monthly mean values in the first half of the year than in the second half. Mean annual d-excess remained constant over the whole long-term period, with a tendency for monthly mean d-excess values to decrease in the first half of the year and increase in the second half due to the influence of air masses originating from the eastern Mediterranean. Changes in the stable isotope composition of precipitation thus resembled changes in the temperature, the circulation pattern of air masses, and the precipitation regime. A local meteoric water line was obtained using different regression methods, which did not result in significant differences between nonweighted and precipitation-weighted slope and intercept values. Deviations from the Global Meteoric Water Line GMWL (lower slopes and intercepts) were observed in two recent periods and could be explained by changes in climate parameters. The temperature gradient of delta18O was 0.33 ‰/°C. The tritium activity concentrations in precipitation showed slight decreases during the last two decades, and the mean A in the most recent period, 2012–2018, was 7.6 ± 0.8 Tritium Units (TU).

Item Type:	Article
Uncontrolled Keywords:	precipitation; Zagreb; Croatia; stable isotope ratios; 2H/1H; 18O/16O; deuterium excess; tritium; LMWL; delta18O-temperature relation
Subjects:	NATURAL SCIENCES > Physics NATURAL SCIENCES > Interdisciplinary Natural Sciences NATURAL SCIENCES > Interdisciplinary Natural Sciences > Environmental Science
Divisions:	Division of Experimental Physics
Depositing User:	Ines Krajcar Bronić
Date Deposited:	14 Jan 2020 13:57
URI:	http://fulir.irb.hr/id/eprint/5293
DOI:	10.3390/w12010226

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